Optical printer

ABSTRACT

An optical printer having a rotating character font, a curved image receiving surface and a lens. The lens is moved incrementally through an arc by a stepper motor to project selected characters from the character font along a line on the image receiving surface. A damping system is provided to control undesired movement in the lens.

United States Patent [191 i Walstrom Aug. 28, 1973 OPTICAL PRINTER v [75] Inventor: Leslie R. Walatrom, Excelsior, Minn.

[73] Assignee: Fabri-Tek Incorporated,

Minneapolis, Minn.

221 Filed: Feb. 1a, 1972 211 App1.No'.:2 27,39l

[52] us. C1 ..9s/4.s n

i [51] Int. Cl B4lb 21/20 [58] Field of Search 95/4.5

[56] References Cited UNITED STATES PATENTS 3,585,296 6/1971 Martin ..95/4.5

3,188,929 6/1965 Higonnet 95/45 3,466,991 9/1969 Hoffmann 95/4.5 3,183,806 5/1965 O'Brien 95/4.5

Primary Examiner-John M. l-loran Attorney-Wayne A. Sivertson ABSTRACT I An optical printer having a rotating character font, a

curved image receiving surface and a lens. The lens is moved incrementally through an are by a stepper motor to project selected characters from the character font along aline on the image receiving surface. A damping system is provided to control undesired movement in the lens.

16 Claims, 5 Drawing Figures Patented Aug. 28, 1973 Z'Sheets-Sheet 2 L 1 INPUT REGISTER COMPARATOR I CHARACTER COUNTERiI STEPPER MOTOR PAPER FEED Y 57 FLASH DURATION FLASH GNIT ON 90 v STEPPER MOTOR CONTROL 0 I. OPTICAL PRINTER BACKGROUND OF THE INVENTION There are many prior art devices which are capable of optically producing a line of print from an input re cord (a punched tape, for example). The projection systems of these devices commonlyemploy a rotating character font of a disc or cylindrical configuration and a lens system for projecting a selected character from the character font onto an image receiving surface.

To achieve a side by side relationship fromone projected character to the next, the prior art devices have utilized highly complex mechanisms for moving one or more of the projection system elements relative to the others. Some have moved a rotating character font relative to the lens system. This requires highly complex amount of travel which even further complicates the motion imparting mechanism. Other systems have left the character font stationary while moving-the optical system and image receiving surface relative to one another. Again, the necessary correspondence in movement of the two elements relative to each otherha's re- I quired the use of highly complex mechanisms.

SUMMARY or TIIE INVENTION The present invention provides a highly efficient and reliable optical printer having a character font and image receiving surface which are stationary relative to each other. An optical member (a single .lens in the embodiment described herein) is moved along an are between the character font and image receiving surface for projection of a series of selected characters from the character font onto the image receiving surface. The optical member moves in increments such that itis stationary during projection and moves between projections to position itself for projection of the next se lected character. The image being projected is always in focus because the location of the image receiving surface is determined by the focal distance of the optical member. A stepper motor is used to drive the opti-' cal member and a damping system is provided for controlling undesirable movement in the optical member.

OBJECTS OF THE INVENTION An object of the present invention is the provision of a highly reliable and efficient optical printer.

Another object of the presentinvention is to provide an optical printer wherein the movement of the projection elements relative to one another is easily controlled.

' Av further object of the present invention is the provi- FIG. 1 shows a portion of the projection system of a preferred embodiment of the present invention;

FIG. 2 shows the remaining portion of the projection system in the embodiment of FIG. 1;

FIG. 3 shows a preferred embodiment of the mechanism for forming the image receiving surface;

FIG. 4 shows a detail of the mechanism of FIG. 3; and

FIG. 5 is a block diagram of an optical printer controlled in accordance with the principles of the present invention.

Referring now to FIG. 1, a portion of a preferred embodiment of the projection system of the present invention is shown. Specifically, a base plate l0 in phantom) is shown to which all of the projection system elements relate.

A stepper motor 12 is mounted on the underside of the base plate 10 by means of a bracket 11. A sprocket 14 is positioned on the output shaft of the stepper motor 12. Spaced from the stepper motor 12, and mounted on top of the base plate 10, is a lens supporting member in the form of a lever arm 15 This lever arm 15 is pivoted at one end about a point 16 and carries a lens 17 adjacent to its other end. Aprojection 26 of the lever arm 15 passes to the underside of the base plate 10 through an arcuate slit 27.

The output of the stepper motor 12 is transmitted to the lens 17 through a continuous multi-section loop 19. The forward section 20 of the loop 19 passes over pulleys 23 and a block 24 and is attached to the projection 26 of the lever arm 15. This section 20 of the loop 19 may be made of Mylar or any other material of similar properties.

, The rearward section 21 of the loop 19 is a link chain. This link portion 21 is-intended to mesh with the sprocket teeth of the stepper motor sprocket 14. Thus, when the stepper motor 12 is energized its output will be transmitted by the sprocket 14 to the loop 19 which in turn will act upon the projection 26 of the lever arm 15 The lever arm 15 will pivot about point 16 and the lens 17 will travel incrementally along a generally circular arc corresponding to the slit 27 in the base plate 10. It should be noted that the loop 19 is attached to thelever arm 15 at the end away. from the pivot point 16. This allows a very positive control over the movement at the lever arm 15 and, thus, the lens 17 As the lens 17 moves,the forward section 20 of the loop 19 is caused to pass over and be in contact with the block 24. Friction exists between them by virtue of It can be seen that the lens is moved in discretesteps I along-its arc with undesirable motion being eliminated bythe friction between the friction block 24 and the loop 19. The friction block 24 may be made of Delrin or any other material of suitable properties.

Located beneath the base plate 10, on a supply roller 29, is a roll of photosensitive paper '30. It has been found that Kodak linagraph direct print paper, Type 1895 is suitable for use in the embodiment here described although any other similarly suited photosensitive material may also be utilized. The paper is fed off the supply roller 30 to pass between a driving roller 31 and an idler roller 32. The driving roller 31 is driven through a clutch 33 by a rotary solenoid 34 to feed an amount of paper equivalent to one line height.

After leaving the rollers 31 and 32, the paper is formed into an arc (in a manner to be described below) and lies behind an arcuate light shield 36. The light shield 36 has an exposure slit 37 positioned such that characters projected by the lens 17 fall on'the photo'- sensitive paper lying within the exposure slit 37. The

are of the photosensitive paper lying within the exposure slit 37 is defined by the focal distance of the lens 17. That is, as the lens steps along its arc, the distance from the lens 17 to the point on the photosensitive paper which will receive the projected image is a constant equal to the focal distance of the lens 17.

A fluorescent light source 38 is positioned outside the exposure area to facilitate the development of the images projected onto the photosensitive material. This light source 38 is not necessary as the paper will develop itself in normal room light but it has been found to be expedient in that it makes the images more quickly available to an interested party.

Mounted on top of the base plate are a left margin microswitch 40 and a right margin microswitch 41 which generate a signal to indicate that the lever arm has arrived at one of the respective margins. The use of these signals will be explained more' completely below.

Referring now to FIG. 2, there is again shown the base plate 10 with the remainder of the projectionsystem mounted thereon. A character font, which in this embodiment takes the form of a character disc 44, is arranged to be driven continuously at a constant speed by means of a synchronous motor 46. The character disc 44 is opaque with a series of transparent alphanumeric characters 48 forming a generally circular arrangement thereon. A series of timing marks 49 are arranged adjacent to the characters 48 on a one to one basis. That is, there is one timing mark for each character. The timing marks 49 are also translucent. In addition to the characters 48 and timing marks 49, the character disc 44 also carries one or more translucent resetting marks 50. The number of re-setting marks 50 is determined by the number of character sets on the character disc-44. There are two re-setting marks 50 shown here in that the preferred embodiment employs two complete character sets on the character disc 44. One re-setting mark 50 is placed at the beginning of each character set and its presence is'detected by a photocell 52. A second photocell 53 detects the passing of each of the timing marks 49. A light source for the photocells 52 and 53 is located on the opposite-side of the character disc 44 and is shown in FIG. 2, in phantom, as element 54. The use of the signal generated by the photocells 52 and 53 will be explained more fully below. g i v Located adjacent to the character disc 44 is a source of high intensity light 55. This light source may be a Xenon tube or any other suitable light source capable of intermittently emitting high intensity light. A character mask 56 is used to shield the projection system from the light produced by the light source 56 while presenting an image of one character at a-time to the lens 17. This is accomplished through an aperture 57 in the character mask 56 whose dimensions are such that only one character is visible to the lens 17 through the aperture 57 at any one time. By flashing the light source 55 at the instant a selected character on the character disc 44 is in position behind theaperture 57, that character.

will appear as a stationary image to the lens 17. It should be noted that the pivot point 16 of the lever arm 15 lies directly below and generally within the plane of the character disc 44.

Referring now to FIG. 3, there is shown more completely the system for feeding paper and forming it into an arc. As described above, the paper is fed by means of a rotary solenoid 34 acting through a rotary clutch 33 to drive a roller 31. An idler roller 32 (here shown folded away for clarity) is employed to hold the paper against the roller 31. A stop 60 limits the travel of the clutch 33 by acting upon a projection 61 of the rotary clutch 33. The stop 60 is adjustable in that it is threaded into a block 62 such that by merely tumig the stop 60 one way or the other the clutch 33 can be allowed to travel more or less before its projection 61 contacts the stop 60.

A second projection on the clutch 33 (not shown) acts upon a linkage 64. The linkage 64 is pivoted generally at its center 67 to rotate with a rod 63. When the clutch moves, its secondprojection acts on the linkage 64 causing it to turn me clockwise direction. At the top end of the linkage 64, a bale 65 is positioned to be engaged by linkage 64 as it rotates. This bale 65 is in the form of a generally circular arc and is spring biased by means of springs 66 toward the paper. The casing behind the paper (the back of light shield 36) is formed in an are generally similar to that of the bale 65. Thus when the bale 65 is urged into contact with the paper by the spring 66, the paper is caused to conform to the arc of the bale and easing. When the rotary solenoid 34 is energized, the rotary clutch 33 acts on the driving roller 31 to cause more paper to be fed and at the same time causes the bale 65 to be disengaged from the paper through the action of the linkage 64. When the solenoid 34 is de-energized, the bale 65 again returns to contact the paper and form it into an arc.

Referring now to FIG. 4, there is shown a second linkage 68 attached to rotate with the rod 63. This linkage 68 controls the amount of paper fed by limiting the travel of the, driving roller 31. A gear 39 is attached .to rotate with the roller 31. When the linkage 64 is rotated by the solenoid 34, this motionis transmitted to the linkage 68 and the bottom portion 70 of the linkage 68 is brought into contact with one of the teeth on the gear 69. Further rotation of the roller 31 is prevented and the paper feed is stopped. A second indexing means is provided through a detent 72 which is a ball type member adapted to fit between the teeth of the gear 69. Referring now to FIG. 5, there is shown a block diagram of the control system of the present invention. The circuitry and electronics involved in controlling the optical printer of the present invention are all-well known and in no way form a part of this invention. They are explained here only for the purpose of clarity and it is to be understood that other control functions may be included within the system, such as means for checking the parity of the input data as well as a means for determining the validity of a particular code signal. In addition, although only one line is shown between different control functions, it is to be understood that these lines are intended to indicate the flow of control signals between control functions which may require only one or a plurality of lines. Also, the reader is not intended to be a part of this invention and is included by way of explanation only. The reader 80 may comprise a star wheel or any other device which is catant speed (3600 rpm, for example). The resetting pho- I tocell 52 signals the beginning of a character set on the character disc each time a re-setting mark 50 passes (every half revolution in the embodiment shown and described). This signal is passed to the character counter 81 and to the input register 82. The signal to the input register 82 is an indication that the system is ready to accept a bit of data while in the instance of the character counter 81 it signals the beginning of a new character set. A signal is called from the character reader 80 by the input register 82 upon receiving the signal from the re-setting photocell 52.

Signals from the timing and re-setting photocells 53 and 52 are transmitted to the character counter 81 which simply keeps track of the position of the character disc 44 and generates a signal indicative of which character on the disc 44 is in the position of the photocell 53. A comparator 83 reads the signals from the input register 82 and the character counter 81 and, when the signals correspond, a signal is sent to the print control 85. The print control 85 comprises a phase adjustment 86 to compensate for the travel time of a particular character from the position of the photocell 5 3 to the aperture 57 in the character mask 56. Means are also provided to control the duration of the flash (control function 87) dependent upon, among other things, the sensitivity of the photosensitive paper and the speed of the character disc' 44.

At the time that the light source 55 is ignited through a flash ignition control 88, a signal is sent to the stepper motor control 90 which will cause the stepper motor 12 to move the lens 17 one increment following the exposure of the selected character. This increment corresponds to one character width (including spaces) so that the characters are aligned and evenly spaced in a side by side fashion. When a complete line has been printed, the right margin microswitch 41 will generate a signal to the input register 82 to prevent the acceptance of new data, signal the paper feed control function 91 for afeed of a new line of paper and will cause the stepper motor to reverse its direction and return to the left margin. Upon return of the lens 17 and lever arm tothe left margin, the left margin microswitch 40 will signal the input register 82 to-accept new data and again reverse the stepper motor 12 to sweep incrementally across a line.

' With two character sets on the characterdisc 44 and the characterdisc 44 rotating at 3600 rpm, the system is capable of asynchronously printing up to 60 characters per second. Bychanging the speed of rotation and- [or the number of character sets, this speed maybe increased or decreased dependent upon the requirements an optical means having a focus;

a supporting means comprising a lever arm pivoted at one end about a point in the plane of the character disc and supporting the optical means at its other end;

means operatively connected to the lever arm adjacent said other end for moving the optical means in an arc; and

an image receiving surface formed along a line defined by the focal distance of the optical means. 2. The optical printer of claim 1 wherein the means for moving the optical means comprises a stepping motor.

3. The optical printer of claim 2 wherein the means for moving the optical means further comprises a continuous loop means, the output of the stepping motor being transmitted to the supporting means through the loop means.

4. The optical printer of claim 1 further comprising means for damping the motion of the optical means.

5. The optical printer of claim 4 wherein the damping means comprises a friction block located contiguous to the loop means, the damping action being provided by friction between the friction block and the loop means. 6. The optical printer of claim 1 wherein the optical means moves in steps in generally circular arc about the character font. 8 I

7. The optical printer of claim 6 further including means for damping the motion of the optical means. 8. An optical printer which comprises: 1 a source of intermittent high intensity light;

a character font comprising a planar character disc adjacent said light source;

' an optical means having a focus;

a supporting means comprising a lever arm pivoted at one end about a point within the plane of the character disc and supporting said optical means at its other end;

a character mask positioned between the character font and-the optical means such that only one character on the character font is visible to the optical means; I

an image receiving surface;

means for sensing the position of the characters on the character font relative to the character mask;

means for energizing the light source when a preselected character is in position for projection onto the image receiving surface; and

means acting upon said other end of the lever arm for moving the optical means in an arc, the image receiving surface being formedalong a line defined by the focal distance of the optical means as it moves through its arc.

9. The optical printer of claim 8wherein the means for moving the optical means comprises a stepper mo tor.

10. The optical printer of claim9 wherein the means for moving the optical means further comprises a loop means, the output of the stepper motor being transmitted to the optical means through the loop means acting upon the supporting means.

11. The optical printer of claim 10 further comprising means for damping the motion of the optical means.

provided by friction between the friction block and the loop means.

13. The optical printer of claim 8 further comprising I means for damping the motion of the optical means.

14. The optical printer of claim 13 wherein the means for moving the optical means comprises a loop means.

ing means for damping the motion of the optical means.

95 -UNITED STATES PA'IENT'OFFICE f- V g 4) 4 e 1 I n I? Q CLRHFICATE 01* CORRluCTlON Patent No.1 3 '4E4 I. Dated August 28, 1973 Inventofls) LeslieR; Walstrom It is certified-that eritor appears the above-identified patent I and that said Letters Patent'are hereby co 'rected as shown below:

Column 1, line 44 39 should be 69- Column 6, line 2 7 insert --a-- between in generally. Column 6 line 67 """dam'pe rf" should be -c 1amping-' Signed and-seeled" this 25th day of December i973.

(SEAL) Attest:

"EDWARD M.FLETCHER,JR. RENE-ID. TEGTMEYER I K Attesting Officer e f Acting Commissioner of Patents 1 l i I I I 2 7 UNITED STATES PA'TENT OFFICE 5 IQ) I I '"w i ,1 t

Gill-TEETHCA;TE O CORRECTTGN' Iatent N o. 3,754,452 Dated August 23, 1973 Inventor(s) Leslie R. Walstrom Itis certified that ertor appears inthe above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 44, 39 should be 69 Column 6, line 27, insert abetween in generally. Column 6, line 67, "damper" should be -damping.

Signed and sealed this ZEth day of December 1973.

(SEAL) Attest:

EDWARD M.FLETCI-]IER,JR. V RENE D. -TEGTMEYER Attesting 'Offieer=- r Acting Commissioner of Patents 

1. An optical printer which comprises: a character font comprising a planar character disc; an optical means having a focus; a supporting means comprising a lever arm pivoted at one end about a point in the plane of the character disc and supporting the optical means at its other end; means operatively connected to the lever arm adjacent said other end for moving the optical means in an arc; and an image receiving surface formed along a line defined by the focal distance of the optical means.
 2. The optical printer of claim 1 wherein the means for moving the optical means comprises a stepping motor.
 3. The optical printer of claim 2 wherein the means for moving the optical means further comprises a continuous loop means, the output of the stepping motor being transmitted to the supporting means through the loop means.
 4. The optical printer of claim 1 further comprising means for damping the motion of the optical means.
 5. The optical printer of claim 4 wherein the damping means comprises a friction block located contiguous to the loop means, the damping action being provided by friction between the friction block and the loop means.
 6. The optical printer of claim 1 wherein the optical means moves in steps in generally circular arc about the character font.
 7. The optical printer of claim 6 further including means for damping the motion of the optical means.
 8. An optical printer which comprises: a source of intermittent high intensity light; a character font comprising a planar character disc adjacent said light source; an optical means having a focus; a supporting means comprising a lever arm pivoted at one end about a point within the plane of the character disc and supporting said optical means at its other end; a character mask positioned between the character font and the optical means such that only one character on the character font is visible to the optical means; an iMage receiving surface; means for sensing the position of the characters on the character font relative to the character mask; means for energizing the light source when a preselected character is in position for projection onto the image receiving surface; and means acting upon said other end of the lever arm for moving the optical means in an arc, the image receiving surface being formed along a line defined by the focal distance of the optical means as it moves through its arc.
 9. The optical printer of claim 8 wherein the means for moving the optical means comprises a stepper motor.
 10. The optical printer of claim 9 wherein the means for moving the optical means further comprises a loop means, the output of the stepper motor being transmitted to the optical means through the loop means acting upon the supporting means.
 11. The optical printer of claim 10 further comprising means for damping the motion of the optical means.
 12. The optical printer of claim 11 wherein the damper means comprises a friction block located contiguous to the loop means, the damping action being provided by friction between the friction block and the loop means.
 13. The optical printer of claim 8 further comprising means for damping the motion of the optical means.
 14. The optical printer of claim 13 wherein the means for moving the optical means comprises a loop means.
 15. The optical printer of claim 8 wherein the optical means moves in steps in a generally circular arc about the character font.
 16. The optical printer of claim 15 further comprising means for damping the motion of the optical means. 